Design Factorial design is employed where more than one independent variables are involved in the investigation. Factorial designs may involves several factors. (E) Small N Design We have briefly mentioned various experimental designs which are termed as large N group designs. In all large N group designs, the number of subject in classroom situation. In many instances, the psychologist or teacher is faced with situations in which large N is not possible, for example delinquency, problem of indiscipline etc. with the introduction of statistics in psychology, it is possible to conduct scientific research on small N group.